A variety of topically-applied skin treatment products are known. Typically, such products are applied by massaging or rubbing into the skin with the fingers or sponge-type applicator. Other methods of application are also known, including aerosol spraying, non-aerosol pump spraying, and electrostatic spraying. For example, electrostatic spraying of skin treatment agents is disclosed in U.S. Pat. No. 5,494,674, issued to Barnett et al. on Feb. 27, 1996.
Electrostatic spraying of topical materials has been proposed as a means for more efficient consumption and product activity, control over application, ease and cleanliness/hygiene of application, and even coverage.
In particular, the art has described electrostatically-sprayable formulations which comprise a single, semi-conductive phase which is accomplished by modifying the conductivity of typically insulating fluids by blending with conductive fluids like ethanol. Such systems are essentially continuous in regard to their electrical resistivity in that the conductive and insulating fluids form a single phase.
While a variety of topical compositions have been provided, there is an ongoing need to improve cosmetic compositions to impart good coverage yet a natural appearance. There is also an ongoing need to improve delivery of skin care compositions in a non-irritating and efficient manner. For example, it is desirable to administer topical skin care actives uniformly to the skin, so as to maximize efficacy. Furthermore, there is an ongoing need to maximize formulation capability in order to improve esthetic and/or functional properties of topical compositions.
The present invention relates to novel methods of treating the skin by electrostatically spraying a topical composition on the skin, wherein the composition comprises an emulsion having an insulating, external phase and a conductive, internal phase. That such compositions can be electrostatically sprayed is surprising since the art has heretofore described essentially electrically-continuous systems.
This surprising development allows for wider formulation of electrostatically sprayable systems. That is, the formulation of essentially electrically continuous systems is limited by the need to maintain the electrical continuity of the system. On the other hand, in the present invention it is possible to utilize different levels of polar and non-polar-soluble or dispersible materials to thereby improve the benefits of the composition. In addition, incorporation of such ingredients wherein the non-polar material, e.g., nonpolar silicones or hydrocarbons, is in the external phase provides improved tactile sensation upon application and tends to reduce the irritation potential of volatile materials which may be incorporated into the internal phase. It is believed that the external, insulating phase insulates such potentially irritating materials from the skin while the product dries on the skin.
It has also been found that when powder materials (e.g., pigments) which are dispersible in the external phase, and not substantially in the internal phase, are incorporated into the emulsion, a “clustering” phenomena of powder results which makes the apparent droplet size (i.e., the droplet size perceived by the eye once the product has dried), smaller than the actual droplet size which is sprayed. Such smaller apparent droplet sizes tend to provide better integration of the product with the bare skin leading to a more natural look. This ability to integrate with the bare skin also enables the use of broader range of shade palettes while maintaining a natural appearance. In contrast, when pigments are incorporated into essentially single phase, semi-conductive compositions, the pigments are generally evenly distributed throughout the sprayed droplets. When such compositions are sprayed, the apparent droplet size approximates the droplet size actually sprayed.